Labconco Purifier Filtered PCR Enclosures 3970425 - Manual (Page 34)

Chapter 6: Maintaining Your Filtered PCR Enclosure
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The circuit board provides power to the sensor and also contains a “safe (green)”
and “alert (red)” airflow LED indicators, as well as a “SILENCE ALARM” button
to quiet the audio alarm. When first powered up, the Printed Circuit Board (PCB)
will light both red and green LED indicators and sound the alarm to indicate it is
working. After 5 seconds, the air monitor will indicate either good or bad airflow
based on what the connected airflow switch detects. For low airflow, the unit will
wait for 10 seconds after low indications before it sounds both the audio alarm and
the red “alert” LED indicator. If the “SILENCE ALARM” button is pressed, the
audio alarm will be silenced, but the red “alert” LED will remain on. The alarm is
silenced indefinitely unless an airflow change is detected. If safe airflow is later
detected for 10 seconds, the green “safe” LED will be lit and the “alert” (red) LED
will be shut off. At any time the airflow is safe/good, one can press the SILENCE
ALARM test button and the audio alarm and the red LED will turn on as long as
this button is held down. The PCB has also a two-pin connector for use as an
external output with isolated relay contacts that close when the red/alert LED is lit
(low airflow). These relay contacts are not affected by the “SILENCE ALARM”
button.
The PCB is mounted behind the front panel using standoffs and an appropriate
label is used to highlight the “SILENCE ALARM” button with clear areas for the
red and green LED’s.
By special order, the PCB can be prepared as a factory special with an additional
connector for the following external inputs, and having the following possible
functions:

External Alarm allows an external signal to sound the alarm from the building
airflow system of a failed condition.
 Alarm Disable allows an external signal to prevent a “low” airflow alarm from
occurring.

Night Setback allows an external signal to prevent a “low” airflow alarm from
occurring (not any different from Alarm Disable above other than the
terminology.)

Contact Labconco for ordering information on this special PCB.
Calibration
1. Ensure the flow switch and alarm circuit board are installed and
operational.
2. Allow the enclosure to operate for at least two minutes.
3. If factory installed, the monitor will alarm at 30±10 fpm downflow velocity
with the average outflow velocity set at 85±10 fpm.
4. To change the factory setting, set the downflow velocity to the desired
alarm condition using the speed control adjustment procedure outlined in
Chapter 6. Once the alarm condition is set, use a small screwdriver to turn
the adjustment screw on the airflow switch counterclockwise (facing the
screw) until the “low” airflow red LED lights and the audible flow alarm
sounds.